1. Field of the Invention
The present invention relates to novel cerium (IV) oxidic compounds and to the preparation and applications thereof, and, more especially, to novel cerium (IV) oxidic compounds that are soluble in organic solvents, notably the hydrocarbons, or are convertible into cerium (IV) oxidic compounds that are soluble in such hydrocarbons.
2. Description of the Prior Art
It is known to this art that cerium serves as a catalyst for numerous applications. In particular, it is useful for catalyzing the crosslinking of film-forming compositions which dry via atmospheric oxidation, e.g., paint films, and it has been described as a catalyst for the oxidation of combustion residues and exhaust gases of hydrocarbon fuels, e.g., diesel fuels, as described in U.S. Pat. No. 4,522,631.
For these various applications, it is important to produce cerium compounds in the cerium (IV) valence state, which is often the catalytically active state. Such cerium (IV) compounds are soluble in organic solvents, stable, and can be stored at high cerium concentrations.
U.S. Pat. No. 4,599,201 to Gradeff et al, and counterpart EP-A-0,093,627, both assigned to the assignee hereof, describe the synthesis of ceric carboxylates which are soluble in organic solvents, from a solution of a cerium (III) compound which is oxidized in an organic medium. Although this process presents several advantages, it also presents the following disadvantages:
(1) the final products obtained are ill-defined and in particular comprise a mixture of cerium (III) and cerium (IV) values in which the proportion of Ce(IV) is not above 75%;
(2) the solutions obtained are extremely viscous and their long term stability is doubtful;
(3) hydrogen peroxide must be used; and
(4) a fraction of the cerium values is lost, in the form of water-soluble byproducts.